In-Game Description

The knights of the ancient kingdom of Balder
wielded these rock-solid, long swords which
are excellent for thrust attacks.
Balder was the home of a Knight King Rendal,
but the kingdom was reduced to ruins after
a widespread outbreak of Undead.

Alternatively, one can start from the Sunlight Altar bonfire (near the Altar of Sunlight in Undead Parish). There are two Balder Knights wielding the Balder Side Sword guarding the entrance of the Undead Parish church, and a third one near the wooden plank bridge outside the church. This location is accessed earlier than Sen's Fortress.

This is an exceptional Straight Sword for DEX builds, as its scaling can reach an A bonus when fully upgraded. Its moveset is also great, with an incredibly powerful thrust strong attack that has great range and can be followed up.

Key

The Damage stat dictates how much damage the weapon does. The Damage stats for a weapon are W / X / Y / Z:

W is Physical Damage

X is Magical Damage

Y is Fire Damage

Z is Lightning Damage

Each weapon has one or more physical damage types:

Normal

Striking

Slashing

Thrusting

Certain enemies are weak or strong against different types of damage types.

Critical:

The damage bonus for backstabs and ripostes. Thrusting Swords and Daggers get an invisible bonus to critical damage as well.

Durability:

The health of the weapon. The effectiveness of the weapon will severely deteriorate when the durability falls below 30%.

Weight:

The weight of the weapon. Note that carrying over 50% of a character's Equip Burden will reduce the speed of their rolls, while going over 100% will reduce their regular speed to walking and attempts to roll or backstep will leave them momentarily stunned.

Stats Needed:

The Stats Needed determines how high various Stats must be in order to wield the weapon effectively. The Requirement stats for a weapon are W / X / Y / Z:

W is the Strength required

X is the Dexterity required

Y is the Intelligence required

Z is the Faith required

Wielding a weapon without the required Strength and/or Dexterity will incur a penalty to the Physical damage of the weapon, while lower-than-required Magic and/or Faith will reduce the Magic damage of the weapon.

Also keep in mind that a character gains a 50% bonus to Strength by wielding a weapon with both hands, thus reducing the actual Strength required.
For example, a character with 18 Strength can wield a Large Club (Requires 26 Strength) properly if the weapon is held with both hands.
(18 x 1.5 = 27)